The invention provides a composition of matter and a method of its use in preventing unwanted polymerization reactions. The composition comprises an inhibitor and a retarder. The inhibitor is highly effective. The retarder is reliable under extreme and emergency situations. The inhibitor can be an alkylhydroxylamine. The retarder can be a 7-cyano-quinone methide. The combination of the inhibitor and retarder has been found to be far more effective than expected.